Investigation Of Microstructures And Properties Of Polymer Modified Epoxy Asphalts

As one of polymer modified asphalts(PMAs),epoxy asphalt(EA)has been extensively used in the pavement of steel bridge deck due to its excellent performances.Ethylene vinyl acetate copolymer(EVA)and crumb rubber are the most used polymer modifiers in PMAs,which significantly improve the toughness of asphalt.In present thesis,epoxy asphalts were modified by EVA and crumb rubber.The influence of EVA,crumb rubber modified asphalt,also known as rubber asphalt(AR)content and curing conditions on the microstructures and properties of epoxy asphalt were investigated,respectively.First,EVA modified asphalts with different contents of EVA were prepared with different EVA loadings.Then,EVA modified epoxy asphalts were prepared by mixing EVA modified asphalts with epoxy resin and curing agent.The effect of EVA on the micromorphology evolution of EA was investigated by laser scanning confocal microscopy(LSCM)and scanning electron microscopy(SEM).Furthermore,the rotational viscosity,thermal stability and mechanical properties of EA/EVA blends were studied.LSCM observations indicate that EVA/EA blends exist phase-separated microstructures,in which epoxy is the continuous phase and EVA-asphalt is the disperse phase.The formation of crosslinking networks of epoxy resin destroys the physical interaction between EVA and asphalts.Both LSCM and SEM observations show that smaller and well-distributed EVA-asphalt particles form in EA/EVA blends with lower EVA loadings.However,EVA-asphalt particles distribute inhomogeneously in the blends with higher EVA loadings.The addition of EVA increases the viscosity of the neat EA.When the content of EVA is less than 1.90 wt%,the viscosity of EA/EVA blends can satisfy the technical requirements of epoxy asphalt for steel bridge deck pavement.The presence of EVA improves thermal stability.Moreover,the addition of EVA improves toughness of the neat EA.EA/EVA blend with 1.90 wt%EVA has a maximum tensile strength(3.06 MPa),which is 33%higher than that of the neat EA(2.30 MPa).The elongation at break of the neat EA(622%)increases by 14%with an EVA loading of 3.75 wt%.Second,epoxy rubber asphalts(EARs)were prepared by using industrial rubber asphalt instead of base asphalt.The effects of AR concentration on the phase-separated morphology,viscosity,thermal stability and mechanical properties of the neat EP were compared with those of asphalt.LSCM observations reveal that spherical phase-separated structures appear in all EAs.As asphalt content increasing to 60 wt%,phase inversion takes place,in which asphalt becomes the continuous phase with a dispersed epoxy phase.AR particles disperse in the continuous epoxy phase with co-continuous phase-separated structures in EARs with 40 and 50 wt%AR.However,the dispersed AR phase inverts to a continuous phase with a dispersed spherical and co-continuous epoxy phase as AR concentration reaches 60 wt%.The addition of AR increases the viscosity of the neat EP.The viscosity of EAR is higher than that of EA at the same content during the cure reaction.The thermal stability of the neat EP is improved with the incorporation of asphalt and AR.In addition,the thermal stability of EA and EAR increases with the increment of asphalt and AR contents.The presence of asphalt and AR increases the elongation at break of the neat EP,and the elongation at break of EA and EAR increases with the increase of asphalt and AR concentrations.The viscosity and mechanical properties of EAR with 50 wt%AR completely satisfy the technical requirement of hot-mix epoxy asphalt binder for steel bridge deck pavements.Finally,the influence of curing conditions on microstructures and mechanical properties of epoxy rubber asphalts was investigated.The high temperature postcuring improves the mobility of AR,leading co-continuous domains of EAR with 40 wt%AR to convert to spherical domains.High temperature direct curing weakens the dynamic asymmetry between EP and AR,resulting in the appearance of spherical particles in EAR.The addition of asphalt and AR hinders the cure reaction of the epoxy resin.The hindered effect of asphalt and AR increases with the increase of contents.The conversion of epoxy rubber asphalt depends on both AR concentration and curing temperature.High temperature postcuring increases the conversion of EAR.The high temperature postcuring and direct curing improve the thermal stability of EAR.Besides,the thermal stability of EARs increases with the increase of AR contents.High temperature postcuring increases the toughness of EAR.The toughness of both EAR and postcured EAR increases with the increase of AR contents.